Metabolism, nutrition, exercise and temperature regulation
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2015
The energetic equivalent of O2 is the amount of energy released by food for each mol of O2 consumed, and this varies for different substrates. The ratio of the volume of CO2 produced to the volume of O2 used when different nutrients are oxidized is known as respiratory quotient (RQ). An RQ of 0.7 denotes all energy is derived from fat; an RQ of 1, all energy is derived from carbohydrate; and an RQ of 0.85, energy is derived from both fat and carbohydrate (50:50 ratio). An RQ greater than 1 denotes fat synthesis from an excess of carbohydrate. Protein oxidation can be assessed from urinary nitrogen excretion; 1 g of nitrogen denotes the oxidation of 6.3 g of protein, oxygen consumption of 5.9 L of oxygen and production of 4.8 L of CO2.
Nutrition
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The energetic equivalent of O2 is the amount of energy released by food for each mole of O2 consumed, and this varies for different substrates. The ratio of the volume of CO2 produced to the volume of O2 used when different nutrients are oxidized is known as the respiratory quotient (RQ). An RQ of 0.7 denotes all energy is derived from fat; an RQ of 1, all energy is derived from carbohydrate; and an RQ of 0.85, energy is derived from both fat and carbohydrate (50:50 ratio). An RQ greater than 1 denotes fat synthesis from an excess of carbohydrate. Protein oxidation can be assessed from urinary nitrogen excretion; 1 g of nitrogen denotes the oxidation of 6.3 g of protein, oxygen consumption of 5.9 L of oxygen and production of 4.8 L of CO2.
Genetics of Energy Expenditure in Humans
Claude Bouchard in The Genetics of Obesity, 2020
Although the mechanisms linking high fat consumption to increased body fat stores remain to be elucidated, interindividual differences in substrate oxidation, particularly lipid oxidation, are likely to be involved.14 The relative proportion of carbohydrate and lipid oxidized can be determined indirectly by measuring the respiratory quotient (RQ) under standardized conditions. Few studies have addressed the role of genetic factors in substrate oxidation. Three lines of evidence suggest that there may be inherited differences in the propensity to oxidize relatively more carbohydrates or lipids. First, twins studies have shown a greater similarity among MZ twins compared to DZ twins in the RQ measured during submaximal exercise, suggesting a role for heredity in substrate oxidation.3 Second, experimental studies in which MZ twins were submitted to overfeeding or exercise-training suggest a significant within-pair resemblance in the pattern of substrate oxidation following a mixed meal or during submaximal exercise. In a study in which 12 pairs of MZ twins were submitted to a 4.2-MJ (1000-kcal) caloric surplus 6 days a week for a period of 100 days under rigorously controlled conditions of energy intake and activity level,15 significant within-pair resemblance was found for the changes in RQ at rest and for several hours following a mixed meal.16 These results suggest that even when energy intake, macronutrient composition of the diet, and physical activity level are standardized for more than 3 months, some individuals oxidize more fat than carbohydrate, and genetic factors appear to play a role in this phenomenon.
Beat the Heat: Effects of a Motivational Self-Talk Intervention on Endurance Performance
Published in Journal of Applied Sport Psychology, 2018
Antonis Hatzigeorgiadis, Khelifa Bartura, Christos Argiropoulos, Nikos Comoutos, Evangelos Galanis, Andreas D. Flouris
Oxygen Consumption and Respiratory Quotient. For oxygen consumption the analysis revealed a significant Group × Time interaction, Greenhouse-Geisser F(5, 10) = 4.68, p < .05, partial η2 = .28, ϵ = .35. Examination of the pairwise comparisons per time revealed that (a) for the control group VO2 increased from Min 5 to Min 10 (p < .01), then did not change significantly from Min 10 to Min 15 (p = .16), from Min 15 to Min 20 (p = .17), and from Min 20 to Min 25 (p = .11), and decreased significantly from Min 25 to Min 30 (p < .01), and (b) for the experimental group VO2 increased from min 5 to min 10 (p < .01), did not change significantly from Min 10 to Min 15 (p = .92), from Min 15 to Min 20 (p = .32), and from Min 20 to Min 25 (p = 32), and increased from Min 25 to Min 30 (p < .05). Examination of the pairwise comparisons per group showed that there were no significant differences between the two groups at Min 5 (p = .93), at Min 10 (p = .67), at Min 15 (p = .96), at Min 20 (p = .65), at Min 25 (p = .20), and at Min 30 (p = .08). Oxygen consumption throughout the 30 min of cycling exercise is displayed in Figure 3. For respiratory quotient the analysis revealed a nonsignificant Group × Time interaction, Greenhouse-Geisser F(5, 10) = 1.88, p = .17, ϵ = .47.
Triheptanoin Supplementation Does not Affect Nutritional Status: A Case Report of Two Siblings With Adult Polyglucosan Body Disease
Published in Journal of the American College of Nutrition, 2020
Ramona De Amicis, Alessandro Leone, Stefano Ravasenghi, Graziana Scigliuolo, Elena Mauro, Ettore Salsano, Alberto Battezzati, Simona Bertoli
To measure oxygen consumption (VO2) and carbon dioxide production (VCO2) we used an open-circuit ventilated-hood system (Sensor Medics 29, Anaheim, CA, USA). We took the measurements in a thermoneutral environment (ambient temperature 24–26 °C) devoid of external stimuli. At the beginning of each test the calorimeter was calibrated: there were two reference gas mixtures (26% O2 and 74% N2; 16% O2, 4.09% CO2 and 79.91% N2, respectively). Patients were fasted for 12 hours. Data collection time was at least 20 min, with a 5 min run-in time for stabilization and time to allow the patients to get used to the canopy and instrument noise. Steady state was determined by five consecutive minutes in which VO2 and VCO2 variations were less than 10%. Patients were not tested unless they had stable respiratory function for at least 1 h. Averaging the steady state values allowed the determination of 24 h REE, done by using the abbreviated Weir equation (17): REE Kcal/day = (3.941 VO2 mL/min + 1.106 VCO2 mL/min) x 1.44. The ratio VCO2/VO2 gave the Respiratory Quotient (RQ) (18).Biochemical parameters
Effects of nocturnal light exposure on circadian rhythm and energy metabolism in healthy adults: A randomized crossover trial
Published in Chronobiology International, 2022
Youngju Choi, Yuki Nakamura, Nobuhiko Akazawa, Insung Park, Hyo-Bum Kwak, Kumpei Tokuyama, Seiji Maeda
Energy metabolism, including energy expenditure and substrate oxidation levels, was measured in a room-sized metabolic chamber (FHC-15S, Fuji Medical Science Co., Ltd. Chiba, Japan) as previously described (Kayaba et al. 2014; Park et al. 2017). The airtight chamber measured 2.00 × 3.45 × 2.10 m, with an internal volume of 14.49 m3. The chamber was furnished with a bed, desk, chair, and toilet. The temperature and relative humidity of the incoming fresh air were controlled at 25.0 ± 0.5°C and 55.0 ± 3.0%, respectively. Concentrations of oxygen and carbon dioxide in the outgoing air were measured using an online process mass spectrometer (VG Prima δB, Thermo Electron, Winsford, UK). Oxygen consumption, and carbon dioxide production rates were calculated every minute using an algorithm providing an improved transient response (Tokuyama et al. 2009). Energy expenditure; carbohydrate, fat, and protein oxidation; and, respiratory quotient (RQ) were calculated from the rates of oxygen consumption, carbon dioxide production, and urinary nitrogen (N) excretion as previously described (Ferrannini 1988). The rate of N, an index of protein oxidation, was assumed to be constant during calorimetry. Energy expenditure and substrate oxidation levels were calculated by summing up the values of the light exposure and sleeping periods, respectively (light exposure period: 21:00 to 24:00, sleeping period: 24:00 to 07:00).
Related Knowledge Centers
- Alveolar Gas Equation
- Deamination
- Fatty Acid
- Glycerol
- Oxygen
- Respirometer
- Basal Metabolic Rate
- Carbohydrate
- Carbon
- Hydrogen